In accordance with the recent trend of lightness and slimness, multi-functionalization, and high integration of an electronic device, it is required to solve a heat release problem due to an increase in heat density. In addition, heat release is important since it is closely related to reliability and lifespan of a device. Accordingly, various heat radiation materials have been developed, and have been commercially available in forms of a heat radiation pad, a heat radiation sheet, a heat radiation paint, and the like, to assist in or replace for the existing heat radiation apparatuses such as a heat radiation fan, a heat radiation fin, a heat pipe, and the like.
Among them, the heat radiation sheet has been manufactured in forms such as a graphite sheet, a polymer-ceramic composition sheet, a multilayer coated metal thin film sheet, and the like. For instance, the graphite sheet has been advantageously used between substrates configuring electronic circuits, and a plasma display panel (PDP) configuring a plasma television, and the like, since it is lightweight and slim, and has significantly higher thermal conductivity over copper.
However, the graphite sheet has excellent thermal conductivity in a transverse direction (horizontal direction), but thermal conductivity in a longitudinal direction (vertical direction) may not be sufficient.
In particular, the thermal conductivity of the graphite sheet in the transverse direction is about 1,500 kw/m2, which is greater than metals such as copper and aluminum. However, the thermal conductivity of the graphite sheet in the longitudinal direction is about 5 to 10 kw/m2, which is less than that of the graphite sheet in the transverse direction.
Accordingly, when the graphite sheet is used to disperse heat generated in the electronic device, it needs to attach a large area of graphite sheet in order to utilize a heat transfer property of the graphite sheet in the transverse direction, as illustrated in FIG. 1.
When there are a number of limitations in thickness, and relatively small limitation in area, for example, a smart phone, it is possible to use the large area of graphite sheet. However, when there is limitation in area of a component, for example, a vehicle component, it is difficult to apply the large area of graphite sheet for heat radiation of the component.
In order to utilize an excellent heat transfer property in the transverse direction so as to solve the above-described problem, there is a method of reducing the area of the graphite sheet by bending the graphite sheet. However, when bending the graphite sheet, crack occurs in an inside or an outside of the graphite, such that a heat transfer path may be disconnected, and the heat transfer property may be rapidly reduced. Further, even at the time of adding a soft material or an additive to the graphite to provide a soft property to the graphite, there is a problem in that heat transfer performance of a pure graphite material is deteriorated.
Therefore, it is required to develop a graphite component capable of effectively solving a heat generation problem caused in the electronic device without causing crack in the inside or the outside of the graphite.